1. Field
The embodiment relates to a wireless power transmission system having a wireless power transmitter.
2. Background
Various kinds of electronic appliances employ batteries and are driven by using the power charged in the batteries, where the battery of an electron appliance may be exchanged or may be recharged. The electronic appliance may include a contact terminal for making contact with an external charging apparatus in order to charge the battery. The electronic appliance is electrically connected to the charging apparatus through the contact terminal. However, the contact terminal may be exposed to an outside of the electronic appliance, such that the contact terminal may be contaminated or shot-circuited due to moisture. In this case, a contact error may be generated between the contact terminal and the charging apparatus to prevent charging of the battery.
An alternative to a contact terminal, a wireless power transmission system, is a technique of transferring power through space without any wires, and maximizes the convenience of supplying power to mobile appliances and digital home appliances. The wireless power transmission system may save energy through real-time power using control, overcome a spatial restriction on power supply and reduce consuming power by using the recharging of a battery. A scheme of implementing a wireless power transmission system is typically classified into a magnetic induction scheme and a magnetic resonance scheme.
The magnetic induction scheme, which is a contactless energy transmission technique which generates electromotive force at one coil through the medium of a magnetic flux generated by allowing two coils to approach closely to each other and current to flow through the other coil, may utilize a frequency of several hundreds of kHz. The magnetic resonance scheme, which is a magnetic resonance technique which uses an electric or magnetic field without using any electromagnetic waves or electric currents, may have a transmissible distance of several meters or more and use a bandwidth of several tens of MHz.
In power transmission efficiency between a transmitter of transmitting power and a receiver of receiving power, impedance matching and selection of a target receiver in a wireless power transmission system, it is important to generate a voltage required of the wireless power transmission system by varying the voltage of a power supply. However, since the system additionally includes a circuit for sensing the voltages or currents of coils included in a transmitter and a receiver and a circuit for controlling the voltage through communication between the transmitter and the receiver, the volume and the complexity of the system are increased.
In addition, in a wireless power transmitter including the magnetic induction scheme and the magnetic resonance scheme, since the electromagnetic induction scheme and the magnetic resonance scheme are different from each other in the ranges of output voltages and the output types, the wireless power transmitter must employ a transformer driven in the electromagnetic induction scheme and a transformer driven in the magnetic resonance scheme, that is, two independent transformers, so that the cost and the complexity of a circuit design are increased. As the circuit complexity of the wireless power transmission system is increased, the heat and electromagnetic waves generated from the components of the wireless power transmitter may deteriorate the performance of the components. In addition, the heat and electromagnetic waves generated from the components may deteriorate the wireless power receiver.